1. Field of the Invention
The present invention relates to a tandem type hydraulic clutch system including: a first hydraulic clutch for urging a first frictional engagement element by a first urging member connected to a first clutch piston which is driven by a hydraulic pressure applied to a first clutch oil chamber; and a second hydraulic clutch for urging a second frictional engagement element by a second urging member connected to a second clutch piston which is driven by a hydraulic pressure applied to a second clutch oil chamber, the first and second hydraulic clutches being axially juxtaposed.
2. Description of the Prior Art
Such a tandem type hydraulic clutch system is conventionally known from Japanese Patent Application Laid-open No.125164/90.
As shown in FIG. 16, the known tandem type hydraulic clutch system includes a first hydraulic clutch C.sub.1 which has a first clutch piston 02.sub.1 axially slidably fitted to an inner periphery of a clutch drum 01, a first urging member 03.sub.1 axially extending from an outer periphery of the first clutch piston 02.sub.1, and first frictional engagement elements 05.sub.1 which are disposed between the clutch drum 01 and a first rotary member 04.sub.1 and brought into pressure contact with one another by the first urging member 03.sub.1 ; and a second hydraulic clutch C.sub.2 which has a second clutch piston 02.sub.2 axially slidably fitted to an inner periphery of the first urging member 03.sub.1, a second urging member 03.sub.2 axially extending from an outer periphery of the second clutch piston 02.sub.2, and second frictional engagement elements 05.sub.2 which are disposed between the first urging member 03.sub.1 and a second rotary member 04.sub.2 and brought into pressure contact with one another by the second Urging member 03.sub.2.
The known tandem type hydraulic clutch system suffers from the following problem. When the first clutch piston 02.sub.1 and the first urging member 03.sub.1 of the outer first hydraulic clutch C.sub.1 are axially slid, the second clutch piston 02.sub.2, the second urging member 03.sub.2 and the second frictional engagement elements 05.sub.2 are also axially slid in a dragged manner and for this reason an unnecessary friction is generated, resulting in an unstable operation.